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Old 02-22-2010, 06:46 PM   #4 (permalink)
aerohead
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fences

Quote:
Originally Posted by JPTrucker View Post
As I have done my own research on aerodynamics, I have noticed that there is the counter-rotating vortices on each rear corner of a vehicle, that is, the rotation on one side is opposite the rotation on the other side. Having a pickup truck and interested in a half-bed cover, would there be any benefit to having a wind fence on each side of the bed? I am thinking this would help "straighten" out these vortices, and at least keep some air that is coming over the cab from "rolling" down over the edge of the bed toward the rear.

If so, what kind of dimensions and shape should they be? Yes, I have a secondary purpose of a wind fence in mind, but am curious as to whether wind fences would be beneficial and not a detriment. No, I am not thinking in terms of a raised "spoiler" across the bed as some trucks have been seen over the years.

My truck cab height is 20" above the bed rail at the corner, with the inside bed dimensions of 73" by 56".
I believe that counter-rotating vortices are most prominent with pseudo-Jaray/'fast-back' cars with too steep a backlight angle.
Your pickup should be suffering from a very large captured-vortex spinning perpendicular to your line of travel within the open bed.
You might be able to 'tailor' this vortex a bit by modifying the rail height and inclination but to diminish the vortex significantly you'll need to address both the back of the cab and where the 'floor' of the bed is.
Here at the aero forum there are a number of threads dealing with pickup drag reduction which speak directly to your problem.
Search around a bit and see if you don't find something which will help.
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